Alternate Vent/Flue Location—Counterflow
A. Vent/flue pipe
D. Plastic plug—alternate vent/flue location
B. Screw locations (4)
E. Rubber elbow
C. Screw locations (3)
F. Induced draft blower
Alternate Vent/Flue Location—Upflow/Horizontal
A. Rubber coupling
B. Vent/flue pipe
Alternate Combustion Air Intake Location
The alternate combustion air intake location consists of a large,
unobstructed hole (alternate vent connection is aligned with the
induced draft blower). To use the alternate combustion air intake
location, refer to the following steps and the "Alternate
Combustion Air Intake Location" illustration.
1. Remove and save the 4 screws securing the combustion air
intake coupling to the base pan.
2. Remove the 3 screws securing the furnace's internal
combustion air intake pipe to the induced draft blower deck.
3. Remove the combustion air intake pipe from the furnace and
cut the pipe at the base pan coupling.
4. Save the base pan coupling and gasket from the induced
draft blower deck coupling for use in the alternate location.
Discard the remaining pipe.
5. Remove the plastic plug from the alternate combustion air
6. Relocate and install the plastic plug in the standard air intake
location (base pan).
7. Insert the plastic plug (included in the drain kit bag) into the
remaining hole in the induced draft blower deck.
8. With the gasket facing the cabinet side panel and the flange's
flat spot facing forward, secure the combustion air intake
coupling to the cabinet using the screws removed in Step 1
or with field-supplied ³⁄₈" #8 self-drilling screws.
C. Induced draft blower
Be sure not to damage internal wiring or other
components when reinstalling coupling and screws.
9. For nondirect vent installations installed horizontally, a
minimum of one 90° elbow should be installed on the
combustion air intake coupling to guard against inadvertent
NOTE: No elbow is required on the alternate combustion air
intake of upright installations, however, a minimum clearance
of 2" (5.1 cm) is required to assure proper air supply.
10. For direct vent installations, secure field-supplied combustion
air intake pipe directly to the air intake coupling.
NOTE: A PVC coupling or elbow is required on counterflow
Alternate Combustion Air Intake Location—Counterflow
A. Section of pipe to be
D. Plastic plug—alternate combustion air
B. Screw locations (4)
E. Screw locations (3)
C. 2" (5.1 cm) minimum
F. Plastic plug from drain kit bag
Nondirect Vent (Single Pipe) Piping
Nondirect vent installations require only a vent/flue pipe. The vent
pipe can be run horizontally with an exit through the side of the
building or run vertically with an exit through the roof of the
building. The vent can also be run through an existing unused
chimney; however, it must extend a minimum of 12" (30.5 cm)
above the top of the chimney. The space between the vent pipe
and the chimney must be closed with a weather-tight, corrosion-
resistant flashing. For details concerning connection of the vent/
flue pipe to the furnace, refer to "Vent Pipe Installation and
Combustion Air—Standard Furnace Connections" or "Vent Pipe
Installation and Combustion Air—Alternate Furnace
Connections" for specific details.
Refer to the following "Nondirect Vent (Single Pipe) Piping—Vent/
Flue Pipe Terminations" for specific details on termination
Although nondirect vent installations do not require a combustion
air intake pipe, a minimum of one 90° elbow should be attached
to the furnace's combustion air intake if an upright installation
uses the standard intake location, or a horizontal installation uses
the alternate air intake location. This elbow will guard against
inadvertent blockage of the air intake.